Take 1 gallon of lemon or lime-juice, of spec. grav. 1·09, in which
dissolve
1 pound of tartaric acid,
1 pound of oxalic acid, and thicken the solution with
4 pounds of pipe or china clay, and 2 pounds of pulverised gum;
as soon as the gum is dissolved, the mixture must be put
through a searce.